12 NEW YORK STATE MjUSEUM 



efifective in preventing' breeding, as the beetles are de- 

 stroyed before they can deposit many eggs. Arsenate of lead is 

 by far the best poison and should be used at the rate of four pounds 

 (15 per cent arsenic oxid) to fifty gallons of water. Fortunately the 

 beetles are rather local in habit and as a consequence individual 

 trees or groups of trees may be protected to a very large extent 

 even if there are neglected ones in the near vicinity. The local 

 spread of this pest is slow and this should be taken advantage 

 of to the greatest possible extent by keeping the insect in control 

 wherever it occurs, even though the infestation be a small one 

 and the present injury of comparatively little importance. It is 

 a mistake on the part of local authorities to wait till this enemy 

 of the elms has become well established and destructive before 

 repressive measures are undertaken. 



The grubs feed almost exclusively on the under surface of 

 the leaf, rarely occurring" upon its upper side. The first injury 

 is usually on the upper more tender leaves, hence there is great 

 need of spraying the tops of the trees, and in order to kill the de- 

 structive grubs it is essential that the poison be thrown on the 

 underside of the foliage. Spraying with an arsenical poison for 

 the destruction of grubs is satisfactory only when the application 

 is early, as it is hardly advisable to spray for this insect when the 

 grubs are nearly full grown, since they are liable to desert the 

 tree even when slightly underfed and complete their transforma- 

 tions, rather than to eat distasteful foliage. 



The ideal spray for this pest is a fine mist applied to the under 

 side of all the leaves. It is impossilile to throw such a spray ' 

 any distance, and owing- to the great height of most elms, .such 

 treatment is impractical. A moderately coarse spray which can 

 be thrown 25 to 40 feet has been usually employed in connection 

 with ladders or the use of a high tower. The latter is practical 

 only where the streets are fairly level. The recent development 

 in the use of a solid stream and pressures of between 200 and 

 300 pounds for gipsy moth work has greatly reduced the cost of 

 applications in woodlands, and the system is now being applied 

 to shade trees with a corresponding saving in time and expense. 

 This method necessitates the use of more poison, there is in- 

 creased dripping and the throwing of the spray upon the foliage 

 is not so readily controlled. These are grave though not insur- 

 mountable objections, and for the present we are inclined to 

 favor a moderately coarse spray with the use of ladders or a 

 tower as the most practical method of spraying shade trees. 



JH 



